The sense of touch forms an intrinsic part of our real world experience and is naturally associated with physical exploration and contact. In many virtual reality (VR) and computer gaming settings, touch provides physical contact and contributes to participant immersion. While most VR and computer gaming applications rely mostly on providing realistic visual imagery, it is well known that our perception and world model is shaped by an integration of visual, auditory and somatosensory stimuli, in an automatic process known as sensory integration. The body is particularly adept at using sensory combinations to “fill in the blanks” where “like” sensory information will direct and reinforce our percept. Additional information may also be obtained from olfaction (smell) and temperature perceptual information. Current state of the art VR and gaming platforms provide a realistic and vivid audio visual experience. However, very few systems are able to provide touch feedback (or for that matter, olfactory and temperature feedback), greatly diminishing the realism of the VR or gaming experience.
Touch is therefore a critical component in human-computer interface as it enables us to perceive the existence of objects and to handle them appropriately. For example, touch feedback during typing is naturally provided by the conventional keyboard mechanism but is absent on most current “solid” touch-screens, making typing more difficult on those devices. In general, this type of force feedback is known as haptics. Most haptics research has focused on force feedback to the hands, especially in tele-robotic (tele-presence) where technology enables interaction with remote objects. Tactile aspects of touch usually refer to vibratory stimuli (from 0 to about 400 Hz). The skin is particularly sensitive to vibrations, especially at frequencies above 150 Hz. Tactile feedback often uses a body-worn spatial array of vibrotactile actuators (“tactors”) to provide the wearer with patterns of vibration at particular body (or skin) locations that are representative of information, for example, directional cueing (for navigation) or communication patterns.
The body's response to haptic and tactile stimuli is somewhat complex depending on stimulus characteristics, body location, transducer geometry and a large number of psychophysical factors (see for example, Bolanowski, S., Gescheider, G., Verrillo, R., & Checkosky, C. (1988). Four channels mediate the mechanical aspects of touch. Journal of the Acoustical Society of America, 84(5), 1680-1694). For example, tactile spatial acuity, defined to be the two-point discrimination threshold, depends on the skin classification (smooth—such as the hand—or hairy) and also varies over the body. Typically areas linked to exploration (such as the fingers) are much more sensitive than other areas such as the torso or back. Touch receptors in the skin are sensitive to shear, displacement, temperature, and vibration. Typically combinations of receptors are activated by stimuli and their responses combined to be centrally interpreted, classified and characterized, sometimes in non-obvious ways. For example, simultaneous cold and pressure stimuli can combine to produce the percept of wetness.
There are many situations where haptic and tactile feedback is needed to simulate the environment in VR and gaming systems. For example, haptic and tactile feedback may be useful to simulate virtual explosions for indoor virtual training systems; specifically, the force felt from debris strikes from an IED explosion and/or the force felt by a bullet strike would greatly enhance the realism or “presence” of the virtual training experience. In other gaming examples, multiple participants may interact within a virtual combat game and it is desirable to provide tactile feedback to a particular participant who is receiving strikes from bullets, objects and the like.
The theme-park and entertainment industry have a multitude of activities, simulators and rides where haptic and tactile feedback presented to participants would greatly enhance the effect and realism of said activities, thereby enhancing the guest experience.
Many of these applications ideally require that the haptic stimulus be administered remotely to a participant, without additional worn components. Therefore, there is an unmet need for the presentation of haptic and tactile feedback stimuli on one or more participants who are not in direct contact with any objects (such as actuators, force feedback devices and the like) and who are naturally interacting and potentially moving within an activity area. It is also known that haptic stimuli must be provided with precise temporal and spatial characteristics that mimic real haptic and tactile cues and events. Further, this must be done in a safe and effective manner.
Several prior-art actuator technologies have been suggested for use in remote haptic systems. These include air jets, fans, air cannons, wearable actuators (Lindeman, R, Yanagida, Y., Noma, H., Hosaka, K, Wearable Vibrotactile Systems for Virtual Contact and Information Display, Special Issue on Haptic Interfaces and Applications, Virtual Reality, 9(2-3), 2006, pp. 203-213 Vibrotactile Feedback for Handling Virtual Contact in Immersive Virtual Environments,” Lindeman, R. W. and Templeman, J. N., Usability Evaluation and Interface Design: Cognitive Engineering, Intelligent Agents and Virtual Reality, Smith, M. J., Salvendy, G., Harris, D., and Koubek, R. J. (Eds.), Lawrence Erlbaum Associates, Mahwah, N.J., 2001, pp. 21-25.) and ultrasonic radiation force. Air jets are simple but are limited in range due to inherent jet turbulence and aerodynamic drag. The use of ultrasonic radiation force in a haptic system is an intriguing technology that has been successfully demonstrated in remote tactile displays. Dalecki et al. (Dalecki D, Child S Z, Raeman C H, Carstensen E L. Tactile perception of ultrasound. J Acoust Soc Am. 1995; 97(5 Pt 1):3165-70) showed that radiation pressure (in liquids) can provide sufficient force to produce tactile sensory effects. Further research (Masafumi Takahashi, Hiroyuki Shinoda, Large Aperture Airborne Ultrasound Tactile Display Using Distributed Array Units, SICE Annual Conference Taiwan, 2010) used a focused array in air to provide vibrotactile stimuli on the outstretched hand of a participant. However, the system produces extremely low actuation forces at the skin surface and is therefore limited in range and capability. Only 1.6×10−2N force has been reported (Takayuki Hoshi, Masafumi Takahashi, Takayuki Iwamoto, and Hiroyuki Shinoda, Noncontact Tactile Display Based on Radiation Pressure of Airborne Ultrasound, IEEE TRANSACTIONS ON HAPTICS, Vol. 3, No. 3, 2010). Therefore ultrasonic non-contact display systems modulate (Takayuki Hoshi, Daisu Abe, and Hiroyuki Shinoda, Adding Tactile Reaction to Hologram, The 18th IEEE International Symposium on Robot and Human Interactive Communication Toyama, Japan, Sep. 27-Oct. 2, 2009) the applied force to produce a vibrotactile stimulus (at 200 Hz, the most sensitive frequency for human skin on the palm). The effective range of this device is limited to about 20 cm2 area and 40 cm height. Extending the range of this technology is technically challenging; safety concerns limit the energy density (at the skin) to less than 100 mW/cm2 which corresponds to a maximum acoustic radiation pressure of about 6.0×10−1N on the surface of the skin Ultrasonic arrays operating in air are also inefficient (absorption and coupling limit range) and costly. Further, previous systems have relied on focusing to achieve sufficient radiation pressures, which limits the effective sensory spatial area to a very narrow region. So, while theoretically possible, there are many practical barriers to the implementation of ultrasonic radiation technologies into a larger scale (and range) VR haptic system.
Therefore new approaches are needed for the generation of remote haptic and tactile stimuli.
The foregoing discussion reflects the current state of the art of which the present inventor is aware. Reference to, and discussion of, this information is intended to aid in discharging Applicant's acknowledged duty of candor in disclosing information that may be relevant to the examination of claims to the present invention. However, it is respectfully submitted that none of the above-indicated information discloses, teaches, suggests, shows, or otherwise renders obvious, either singly or when considered in combination, the invention described and claimed herein.